51
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Identification of Clostridium cochlearium as an electroactive microorganism from the mouse gut microbiome. Bioelectrochemistry 2019; 130:107334. [PMID: 31352302 DOI: 10.1016/j.bioelechem.2019.107334] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Revised: 07/16/2019] [Accepted: 07/16/2019] [Indexed: 12/11/2022]
Abstract
Microbial electroactivity, the metabolically relevant transfer of electrons between microorganisms and solid conductors, was first discovered for now well characterized model organisms from hypoxic or anaerobic water or sediment samples. Recent findings indicate that the metabolic trait of electroactivity might as well be important within the microbiome of the mammalian gut. Based on a pre-selection from the mouse intestinal bacterial collection five microorganisms originating from diverse parts of the gut were screened for electroactivity. As there is no marker gene for electroactivity, the ability to synthesize cytochromes and metabolize redox-mediators was studied in-silico. Clostridium cochlearium showed highest electroactivity and Lactobacillus reuteri as well as Staphylococcus xylosus show putative electroactivity, as well. The maximum current density of C. cochlearium of 0.53 ± 0.02 mA cm-2 after only 5.2 h of incubation was clearly linked to growth and glucose consumption. Cyclic voltammetric analysis on C. cochlearium revealed a formal potential of the extracellular electron transfer (EET) site of +0.22 ± 0.05 V versus Ag/AgCl sat. KCl (and + 0.42 V versus SHE) and indicates that EET is not based on biofilm formation, but the involvement of either redox-active molecules or planktonic cells. The potential of the gut as habitat for electroactives and their physiological role are discussed.
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52
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Hermans M, Lenstra WK, Hidalgo-Martinez S, van Helmond NAGM, Witbaard R, Meysman FJ, Gonzalez S, Slomp CP. Abundance and Biogeochemical Impact of Cable Bacteria in Baltic Sea Sediments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:7494-7503. [PMID: 31149818 PMCID: PMC6611076 DOI: 10.1021/acs.est.9b01665] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/15/2019] [Accepted: 05/31/2019] [Indexed: 05/19/2023]
Abstract
Oxygen depletion in coastal waters may lead to release of toxic sulfide from sediments. Cable bacteria can limit sulfide release by promoting iron oxide formation in sediments. Currently, it is unknown how widespread this phenomenon is. Here, we assess the abundance, activity, and biogeochemical impact of cable bacteria at 12 Baltic Sea sites. Cable bacteria were mostly absent in sediments overlain by anoxic and sulfidic bottom waters, emphasizing their dependence on oxygen or nitrate as electron acceptors. At sites that were temporarily reoxygenated, cable bacterial densities were low. At seasonally hypoxic sites, cable bacterial densities correlated linearly with the supply of sulfide. The highest densities were observed at Gulf of Finland sites with high rates of sulfate reduction. Microelectrode profiles of sulfide, oxygen, and pH indicated low or no in situ cable bacteria activity at all sites. Reactivation occurred within 5 days upon incubation of an intact sediment core from the Gulf of Finland with aerated overlying water. We found no relationship between cable bacterial densities and macrofaunal abundances, salinity, or sediment organic carbon. Our geochemical data suggest that cable bacteria promote conversion of iron monosulfides to iron oxides in the Gulf of Finland in spring, possibly explaining why bottom waters in this highly eutrophic region rarely contain sulfide in summer.
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Affiliation(s)
- Martijn Hermans
- Department
of Earth Sciences—Geochemistry, Faculty of Geosciences, Utrecht University, 3508 TC Utrecht, The Netherlands
- E-mail:
| | - Wytze K. Lenstra
- Department
of Earth Sciences—Geochemistry, Faculty of Geosciences, Utrecht University, 3508 TC Utrecht, The Netherlands
| | | | - Niels A. G. M. van Helmond
- Department
of Earth Sciences—Geochemistry, Faculty of Geosciences, Utrecht University, 3508 TC Utrecht, The Netherlands
| | - Rob Witbaard
- Department
of Estuarine and Delta Systems, NIOZ, Royal
Netherlands Institute for Sea Research and Utrecht University, 4400 AC Yerseke, The Netherlands
| | - Filip J.R. Meysman
- Department
of Biology, University of Antwerp, 2020 Wilrijk, Belgium
- Department
of Biotechnology, Delft University of Technology, 2628 CN Delft, The Netherlands
| | - Santiago Gonzalez
- Department
of Microbiology and Biogeochemistry, NIOZ,
Royal Netherlands Institute of Sea Research and Utrecht University, 1790 AB Den Burg, Texel, The Netherlands
| | - Caroline P. Slomp
- Department
of Earth Sciences—Geochemistry, Faculty of Geosciences, Utrecht University, 3508 TC Utrecht, The Netherlands
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53
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Molecular underpinnings for microbial extracellular electron transfer during biogeochemical cycling of earth elements. SCIENCE CHINA-LIFE SCIENCES 2019; 62:1275-1286. [DOI: 10.1007/s11427-018-9464-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 12/09/2018] [Indexed: 02/07/2023]
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54
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Assessment of Electron Transfer Mechanisms during a Long-Term Sediment Microbial Fuel Cell Operation. ENERGIES 2019. [DOI: 10.3390/en12030481] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The decentralized production of bioelectricity as well as the bioremediation of contaminated sediments might be achieved by the incorporation of an anode into anaerobic sediments and a cathode suspended in the water column. In this context, a sediment microbial fuel cell microcosm was carried out using different configurations of electrodes and types of materials (carbon and stainless steel). The results showed a long-term continuous production of electricity (>300 days), with a maximum voltage of approximately 100 mV reached after ~30 days of operation. A twofold increase of voltage was noticed with a twofold increase of surface area (~30 mV to ~60 mV vs. 40 cm2 to 80 cm2), while a threefold increase was obtained after the substitution of a carbon anode by one of stainless steel (~20 mV to ~65 mV vs. 40 cm2 to 812 cm2). Cyclic voltammetry was used to evaluate sediment bacteria electroactivity and to determine the kinetic parameters of redox reactions. The voltammetric results showed that redox processes were limited by the diffusion step and corresponded to a quasi-reversible electron charge transfer. These results are encouraging and give important information for the further optimization of sediment microbial fuel cell performance towards the long-term operation of sediment microbial fuel cell devices.
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55
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Cornelissen R, Bøggild A, Thiruvallur Eachambadi R, Koning RI, Kremer A, Hidalgo-Martinez S, Zetsche EM, Damgaard LR, Bonné R, Drijkoningen J, Geelhoed JS, Boesen T, Boschker HTS, Valcke R, Nielsen LP, D'Haen J, Manca JV, Meysman FJR. The Cell Envelope Structure of Cable Bacteria. Front Microbiol 2018; 9:3044. [PMID: 30619135 PMCID: PMC6307468 DOI: 10.3389/fmicb.2018.03044] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 11/26/2018] [Indexed: 11/16/2022] Open
Abstract
Cable bacteria are long, multicellular micro-organisms that are capable of transporting electrons from cell to cell along the longitudinal axis of their centimeter-long filaments. The conductive structures that mediate this long-distance electron transport are thought to be located in the cell envelope. Therefore, this study examines in detail the architecture of the cell envelope of cable bacterium filaments by combining different sample preparation methods (chemical fixation, resin-embedding, and cryo-fixation) with a portfolio of imaging techniques (scanning electron microscopy, transmission electron microscopy and tomography, focused ion beam scanning electron microscopy, and atomic force microscopy). We systematically imaged intact filaments with varying diameters. In addition, we investigated the periplasmic fiber sheath that remains after the cytoplasm and membranes were removed by chemical extraction. Based on these investigations, we present a quantitative structural model of a cable bacterium. Cable bacteria build their cell envelope by a parallel concatenation of ridge compartments that have a standard size. Larger diameter filaments simply incorporate more parallel ridge compartments. Each ridge compartment contains a ~50 nm diameter fiber in the periplasmic space. These fibers are continuous across cell-to-cell junctions, which display a conspicuous cartwheel structure that is likely made by invaginations of the outer cell membrane around the periplasmic fibers. The continuity of the periplasmic fibers across cells makes them a prime candidate for the sought-after electron conducting structure in cable bacteria.
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Affiliation(s)
| | - Andreas Bøggild
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark.,Interdisciplinary Nanoscience Center and Department of Molecular Biology and Genetics, Structural Biology Aarhus University, Aarhus, Denmark
| | | | - Roman I Koning
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Anna Kremer
- Bio-imaging Core, Flemish Institute of Biotechnology (VIB), Gent, Belgium
| | | | - Eva-Maria Zetsche
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Lars R Damgaard
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark
| | | | | | | | - Thomas Boesen
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark.,Interdisciplinary Nanoscience Center and Department of Molecular Biology and Genetics, Structural Biology Aarhus University, Aarhus, Denmark
| | - Henricus T S Boschker
- Department of Biology, University of Antwerp, Antwerpen, Belgium.,Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Roland Valcke
- Molecular and Physical Plant Physiology, Hasselt University, Hasselt, Belgium
| | - Lars Peter Nielsen
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark
| | - Jan D'Haen
- Institute for Materials Research (IMO), Hasselt University, Hasselt, Belgium
| | | | - Filip J R Meysman
- Department of Biology, University of Antwerp, Antwerpen, Belgium.,Department of Biotechnology, Delft University of Technology, Delft, Netherlands
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56
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Schoeffler M, Gaudin AL, Ramel F, Valette O, Denis Y, Hania WB, Hirschler-Réa A, Dolla A. Growth of an anaerobic sulfate-reducing bacterium sustained by oxygen respiratory energy conservation after O 2 -driven experimental evolution. Environ Microbiol 2018; 21:360-373. [PMID: 30394641 DOI: 10.1111/1462-2920.14466] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 10/25/2018] [Accepted: 10/31/2018] [Indexed: 11/30/2022]
Abstract
Desulfovibrio species are representatives of microorganisms at the boundary between anaerobic and aerobic lifestyles, since they contain the enzymatic systems required for both sulfate and oxygen reduction. However, the latter has been shown to be solely a protective mechanism. By implementing the oxygen-driven experimental evolution of Desulfovibrio vulgaris Hildenborough, we have obtained strains that have evolved to grow with energy derived from oxidative phosphorylation linked to oxygen reduction. We show that a few mutations are sufficient for the emergence of this phenotype and reveal two routes of evolution primarily involving either inactivation or overexpression of the gene encoding heterodisulfide reductase. We propose that the oxygen respiration for energy conservation that sustains the growth of the O2 -evolved strains is associated with a rearrangement of metabolite fluxes, especially NAD+ /NADH, leading to an optimized O2 reduction. These evolved strains are the first sulfate-reducing bacteria that exhibit a demonstrated oxygen respiratory process that enables growth.
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Affiliation(s)
- Marine Schoeffler
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Anne-Laure Gaudin
- Aix Marseille Université, CNRS, LCB, Marseille, France.,GERME SA, Technopôle de Château Gombert, Marseille, France
| | - Fanny Ramel
- Aix Marseille Université, CNRS, LCB, Marseille, France
| | - Odile Valette
- Aix Marseille Université, CNRS, LCB, Marseille, France
| | - Yann Denis
- Aix Marseille Université, CNRS, IMM, Marseille, France
| | - Wagdi Ben Hania
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Agnès Hirschler-Réa
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Alain Dolla
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
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57
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Otte JM, Harter J, Laufer K, Blackwell N, Straub D, Kappler A, Kleindienst S. The distribution of active iron‐cycling bacteria in marine and freshwater sediments is decoupled from geochemical gradients. Environ Microbiol 2018; 20:2483-2499. [DOI: 10.1111/1462-2920.14260] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 04/26/2018] [Accepted: 04/26/2018] [Indexed: 11/30/2022]
Affiliation(s)
- Julia M. Otte
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen Germany
| | - Johannes Harter
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen Germany
| | - Katja Laufer
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen Germany
- Center for Geomicrobiology, Department of BioscienceAarhus University Denmark
| | - Nia Blackwell
- Microbial Ecology, Center for Applied GeosciencesUniversity of Tübingen Germany
| | - Daniel Straub
- Microbial Ecology, Center for Applied GeosciencesUniversity of Tübingen Germany
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen Germany
- Center for Geomicrobiology, Department of BioscienceAarhus University Denmark
| | - Sara Kleindienst
- Microbial Ecology, Center for Applied GeosciencesUniversity of Tübingen Germany
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58
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Marzocchi U, Bonaglia S, van de Velde S, Hall POJ, Schramm A, Risgaard-Petersen N, Meysman FJR. Transient bottom water oxygenation creates a niche for cable bacteria in long-term anoxic sediments of the Eastern Gotland Basin. Environ Microbiol 2018; 20:3031-3041. [DOI: 10.1111/1462-2920.14349] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/27/2018] [Accepted: 06/29/2018] [Indexed: 11/27/2022]
Affiliation(s)
- Ugo Marzocchi
- Department of Chemistry; Research Group for Analytical, Environmental and Geochemistry, Vrije Universiteit; Brussels Belgium
- Center for Geomicrobiology, Section for Microbiology, Department of Bioscience; Aarhus University; Aarhus Denmark
| | - Stefano Bonaglia
- Department of Ecology, Environment and Plant Sciences; Stockholm University; Stockholm Sweden
| | - Sebastiaan van de Velde
- Department of Chemistry; Research Group for Analytical, Environmental and Geochemistry, Vrije Universiteit; Brussels Belgium
- Department of Biology; Universiteit Antwerpen; Antwerpen Belgium
| | - Per O. J. Hall
- Department of Marine Sciences; University of Gothenburg; Gothenburg Sweden
| | - Andreas Schramm
- Center for Electromicrobiology, Section for Microbiology, Department of Bioscience; Aarhus University; Aarhus Denmark
| | - Nils Risgaard-Petersen
- Center for Geomicrobiology, Section for Microbiology, Department of Bioscience; Aarhus University; Aarhus Denmark
- Center for Electromicrobiology, Section for Microbiology, Department of Bioscience; Aarhus University; Aarhus Denmark
| | - Filip J. R. Meysman
- Department of Biology; Universiteit Antwerpen; Antwerpen Belgium
- Aarhus Institute of Advanced Sciences; Aarhus University; Aarhus Denmark
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59
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Abstract
Electron transport within living cells is essential for energy conservation in all respiring and photosynthetic organisms. While a few bacteria transport electrons over micrometer distances to their surroundings, filaments of cable bacteria are hypothesized to conduct electric currents over centimeter distances. We used resonance Raman microscopy to analyze cytochrome redox states in living cable bacteria. Cable-bacteria filaments were placed in microscope chambers with sulfide as electron source and oxygen as electron sink at opposite ends. Along individual filaments a gradient in cytochrome redox potential was detected, which immediately broke down upon removal of oxygen or laser cutting of the filaments. Without access to oxygen, a rapid shift toward more reduced cytochromes was observed, as electrons were no longer drained from the filament but accumulated in the cellular cytochromes. These results provide direct evidence for long-distance electron transport in living multicellular bacteria.
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60
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Cable Bacteria Take a New Breath Using Long-Distance Electricity. Trends Microbiol 2018; 26:411-422. [DOI: 10.1016/j.tim.2017.10.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 10/29/2017] [Accepted: 10/31/2017] [Indexed: 11/18/2022]
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61
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Kawaichi S, Yamada T, Umezawa A, McGlynn SE, Suzuki T, Dohmae N, Yoshida T, Sako Y, Matsushita N, Hashimoto K, Nakamura R. Anodic and Cathodic Extracellular Electron Transfer by the Filamentous Bacterium Ardenticatena maritima 110S. Front Microbiol 2018; 9:68. [PMID: 29467724 PMCID: PMC5808234 DOI: 10.3389/fmicb.2018.00068] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 01/11/2018] [Indexed: 11/13/2022] Open
Abstract
Ardenticatena maritima strain 110S is a filamentous bacterium isolated from an iron-rich coastal hydrothermal field, and it is a unique isolate capable of dissimilatory iron or nitrate reduction among the members of the bacterial phylum Chloroflexi. Here, we report the ability of A. maritima strain 110S to utilize electrodes as a sole electron acceptor and donor when coupled with the oxidation of organic compounds and nitrate reduction, respectively. In addition, multicellular filaments with hundreds of cells arranged end-to-end increased the extracellular electron transfer (EET) ability to electrodes by organizing filaments into bundled structures, with the aid of microbially reduced iron oxide minerals on the cell surface of strain 110S. Based on these findings, together with the attempt to detect surface-localized cytochromes in the genome sequence and the demonstration of redox-dependent staining and immunostaining of the cell surface, we propose a model of bidirectional electron transport by A. maritima strain 110S, in which surface-localized multiheme cytochromes and surface-associated iron minerals serve as a conduit of bidirectional EET in multicellular filaments.
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Affiliation(s)
- Satoshi Kawaichi
- Biofunctional Catalyst Research Team, Center for Sustainable Resource Science, RIKEN, Saitama, Japan
| | - Tetsuya Yamada
- Biofunctional Catalyst Research Team, Center for Sustainable Resource Science, RIKEN, Saitama, Japan.,Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan
| | - Akio Umezawa
- Biofunctional Catalyst Research Team, Center for Sustainable Resource Science, RIKEN, Saitama, Japan
| | - Shawn E McGlynn
- Biofunctional Catalyst Research Team, Center for Sustainable Resource Science, RIKEN, Saitama, Japan.,Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - Takehiro Suzuki
- Biomolecular Characterization Unit, Center for Sustainable Resource Science, RIKEN, Wako, Japan
| | - Naoshi Dohmae
- Biomolecular Characterization Unit, Center for Sustainable Resource Science, RIKEN, Wako, Japan
| | - Takashi Yoshida
- Laboratory of Marine Microbiology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yoshihiko Sako
- Laboratory of Marine Microbiology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Nobuhiro Matsushita
- Department of Materials Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan
| | | | - Ryuhei Nakamura
- Biofunctional Catalyst Research Team, Center for Sustainable Resource Science, RIKEN, Saitama, Japan.,Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
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62
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Li C, Lesnik KL, Liu H. Stay connected: Electrical conductivity of microbial aggregates. Biotechnol Adv 2017; 35:669-680. [PMID: 28768145 DOI: 10.1016/j.biotechadv.2017.07.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 01/01/2023]
Abstract
The discovery of direct extracellular electron transfer offers an alternative to the traditional understanding of diffusional electron exchange via small molecules. The establishment of electronic connections between electron donors and acceptors in microbial communities is critical to electron transfer via electrical currents. These connections are facilitated through conductivity associated with various microbial aggregates. However, examination of conductivity in microbial samples is still in its relative infancy and conceptual models in terms of conductive mechanisms are still being developed and debated. The present review summarizes the fundamental understanding of electrical conductivity in microbial aggregates (e.g. biofilms, granules, consortia, and multicellular filaments) highlighting recent findings and key discoveries. A greater understanding of electrical conductivity in microbial aggregates could facilitate the survey for additional microbial communities that rely on direct extracellular electron transfer for survival, inform rational design towards the aggregates-based production of bioenergy/bioproducts, and inspire the construction of new synthetic conductive polymers.
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Affiliation(s)
- Cheng Li
- Biological and Ecological Engineering, Oregon State University, Corvallis, OR 97333, USA
| | - Keaton Larson Lesnik
- Biological and Ecological Engineering, Oregon State University, Corvallis, OR 97333, USA
| | - Hong Liu
- Biological and Ecological Engineering, Oregon State University, Corvallis, OR 97333, USA.
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63
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Lovley DR. Happy together: microbial communities that hook up to swap electrons. ISME JOURNAL 2016; 11:327-336. [PMID: 27801905 DOI: 10.1038/ismej.2016.136] [Citation(s) in RCA: 177] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 08/29/2016] [Accepted: 09/04/2016] [Indexed: 12/22/2022]
Abstract
The discovery of direct interspecies electron transfer (DIET) and cable bacteria has demonstrated that microbial cells can exchange electrons over long distances (μm-cm) through electrical connections. For example, in the presence of cable bacteria electrons are rapidly transported over centimeter distances, coupling the oxidation of reduced sulfur compounds in anoxic sediments to oxygen reduction in overlying surficial sediments. Bacteria and archaea wired for DIET are found in anaerobic methane-producing and methane-consuming communities. Electrical connections between gut microbes and host cells have also been proposed. Iterative environmental and defined culture studies on methanogenic communities revealed the importance of electrically conductive pili and c-type cytochromes in natural electrical grids, and demonstrated that conductive carbon materials and magnetite can substitute for these biological connectors to facilitate DIET. This understanding has led to strategies to enhance and stabilize anaerobic digestion. Key unknowns warranting further investigation include elucidation of the archaeal electrical connections facilitating DIET-based methane production and consumption; and the mechanisms for long-range electron transfer through cable bacteria. A better understanding of mechanisms for cell-to-cell electron transfer could facilitate the hunt for additional electrically connected microbial communities with omics approaches and could advance spin-off applications such as the development of sustainable bioelectronics materials and bioelectrochemical technologies.
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Affiliation(s)
- Derek R Lovley
- Department of Microbiology, Morrill IV N Science Center, University of Massachusetts, Amherst, MA, USA
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64
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Fernandez-Gonzalez N, Huber JA, Vallino JJ. Microbial Communities Are Well Adapted to Disturbances in Energy Input. mSystems 2016; 1:e00117-16. [PMID: 27822558 PMCID: PMC5080406 DOI: 10.1128/msystems.00117-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 08/16/2016] [Indexed: 11/20/2022] Open
Abstract
Although microbial systems are well suited for studying concepts in ecological theory, little is known about how microbial communities respond to long-term periodic perturbations beyond diel oscillations. Taking advantage of an ongoing microcosm experiment, we studied how methanotrophic microbial communities adapted to disturbances in energy input over a 20-day cycle period. Sequencing of bacterial 16S rRNA genes together with quantification of microbial abundance and ecosystem function were used to explore the long-term dynamics (510 days) of methanotrophic communities under continuous versus cyclic chemical energy supply. We observed that microbial communities appeared inherently well adapted to disturbances in energy input and that changes in community structure in both treatments were more dependent on internal dynamics than on external forcing. The results also showed that the rare biosphere was critical to seeding the internal community dynamics, perhaps due to cross-feeding or other strategies. We conclude that in our experimental system, internal feedbacks were more important than external drivers in shaping the community dynamics over time, suggesting that ecosystems can maintain their function despite inherently unstable community dynamics. IMPORTANCE Within the broader ecological context, biological communities are often viewed as stable and as only experiencing succession or replacement when subject to external perturbations, such as changes in food availability or the introduction of exotic species. Our findings indicate that microbial communities can exhibit strong internal dynamics that may be more important in shaping community succession than external drivers. Dynamic "unstable" communities may be important for ecosystem functional stability, with rare organisms playing an important role in community restructuring. Understanding the mechanisms responsible for internal community dynamics will certainly be required for understanding and manipulating microbiomes in both host-associated and natural ecosystems.
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Affiliation(s)
| | - Julie A. Huber
- The Josephine Bay Paul Center, Marine Biological Laboratory, Woods Hole, Massachusetts, USA
| | - Joseph J. Vallino
- Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts, USA
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65
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Extracellular electron transfer mechanisms between microorganisms and minerals. Nat Rev Microbiol 2016; 14:651-62. [DOI: 10.1038/nrmicro.2016.93] [Citation(s) in RCA: 850] [Impact Index Per Article: 106.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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66
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Bjerg JT, Damgaard LR, Holm SA, Schramm A, Nielsen LP. Motility of Electric Cable Bacteria. Appl Environ Microbiol 2016; 82:3816-21. [PMID: 27084019 PMCID: PMC4907201 DOI: 10.1128/aem.01038-16] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 04/13/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Cable bacteria are filamentous bacteria that electrically couple sulfide oxidation and oxygen reduction at centimeter distances, and observations in sediment environments have suggested that they are motile. By time-lapse microscopy, we found that cable bacteria used gliding motility on surfaces with a highly variable speed of 0.5 ± 0.3 μm s(-1) (mean ± standard deviation) and time between reversals of 155 ± 108 s. They frequently moved forward in loops, and formation of twisted loops revealed helical rotation of the filaments. Cable bacteria responded to chemical gradients in their environment, and around the oxic-anoxic interface, they curled and piled up, with straight parts connecting back to the source of sulfide. Thus, it appears that motility serves the cable bacteria in establishing and keeping optimal connections between their distant electron donor and acceptors in a dynamic sediment environment. IMPORTANCE This study reports on the motility of cable bacteria, capable of transmitting electrons over centimeter distances. It gives us a new insight into their behavior in sediments and explains previously puzzling findings. Cable bacteria greatly influence their environment, and this article adds significantly to the body of knowledge about this organism.
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Affiliation(s)
- Jesper Tataru Bjerg
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Lars Riis Damgaard
- Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Simon Agner Holm
- Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Andreas Schramm
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Lars Peter Nielsen
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
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67
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Li C, Lesnik KL, Fan Y, Liu H. Millimeter scale electron conduction through exoelectrogenic mixed species biofilms. FEMS Microbiol Lett 2016; 363:fnw153. [PMID: 27279626 DOI: 10.1093/femsle/fnw153] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/02/2016] [Indexed: 02/03/2023] Open
Abstract
The functioning of many natural and engineered environments is dependent on long distance electron transfer mediated through electrical currents. These currents have been observed in exoelectrogenic biofilms and it has been proposed that microbial biofilms can mediate electron transfer via electrical currents on the centimeter scale. However, direct evidence to confirm this hypothesis has not been demonstrated and the longest known electrical transfer distance for single species exoelectrogenic biofilms is limited to 100 μm. In the present study, biofilms were developed on electrodes with electrically non-conductive gaps from 50 μm to 1 mm and the in situ conductance of biofilms was evaluated over time. Results demonstrated that the exoelectrogenic mixed species biofilms in the present study possess the ability to transfer electrons through electrical currents over a distance of up to 1 mm, 10 times further than previously observed. Results indicate the possibility of interspecies interactions playing an important role in the spatial development of exoelectrogenic biofilms, suggesting that these biological networks might remain conductive even at longer distance. These findings have significant implications in regards to future optimization of microbial electrochemical systems.
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Affiliation(s)
- Cheng Li
- Department of Biological and Ecological Engineering, Oregon State University, 116 Gilmore Hall, Corvallis, OR 97333, USA
| | - Keaton Larson Lesnik
- Department of Biological and Ecological Engineering, Oregon State University, 116 Gilmore Hall, Corvallis, OR 97333, USA
| | - Yanzhen Fan
- Department of Biological and Ecological Engineering, Oregon State University, 116 Gilmore Hall, Corvallis, OR 97333, USA
| | - Hong Liu
- Department of Biological and Ecological Engineering, Oregon State University, 116 Gilmore Hall, Corvallis, OR 97333, USA
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68
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Trojan D, Schreiber L, Bjerg JT, Bøggild A, Yang T, Kjeldsen KU, Schramm A. A taxonomic framework for cable bacteria and proposal of the candidate genera Electrothrix and Electronema. Syst Appl Microbiol 2016; 39:297-306. [PMID: 27324572 PMCID: PMC4958695 DOI: 10.1016/j.syapm.2016.05.006] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 05/06/2016] [Accepted: 05/09/2016] [Indexed: 11/29/2022]
Abstract
Cable bacteria are long, multicellular filaments that can conduct electric currents over centimeter-scale distances. All cable bacteria identified to date belong to the deltaproteobacterial family Desulfobulbaceae and have not been isolated in pure culture yet. Their taxonomic delineation and exact phylogeny is uncertain, as most studies so far have reported only short partial 16S rRNA sequences or have relied on identification by a combination of filament morphology and 16S rRNA-targeted fluorescence in situ hybridization with a Desulfobulbaceae-specific probe. In this study, nearly full-length 16S rRNA gene sequences of 16 individual cable bacteria filaments from freshwater, salt marsh, and marine sites of four geographic locations are presented. These sequences formed a distinct, monophyletic sister clade to the genus Desulfobulbus and could be divided into six coherent, species-level clusters, arranged as two genus-level groups. The same grouping was retrieved by phylogenetic analysis of full or partial dsrAB genes encoding the dissimilatory sulfite reductase. Based on these results, it is proposed to accommodate cable bacteria within two novel candidate genera: the mostly marine “Candidatus Electrothrix”, with four candidate species, and the mostly freshwater “Candidatus Electronema”, with two candidate species. This taxonomic framework can be used to assign environmental sequences confidently to the cable bacteria clade, even without morphological information. Database searches revealed 185 16S rRNA gene sequences that affiliated within the clade formed by the proposed cable bacteria genera, of which 120 sequences could be assigned to one of the six candidate species, while the remaining 65 sequences indicated the existence of up to five additional species.
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Affiliation(s)
- Daniela Trojan
- Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark.
| | - Lars Schreiber
- Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
| | - Jesper T Bjerg
- Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
| | - Andreas Bøggild
- Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
| | - Tingting Yang
- Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
| | - Kasper U Kjeldsen
- Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
| | - Andreas Schramm
- Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark.
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69
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Rao A, Risgaard-Petersen N, Neumeier U. Electrogenic sulfur oxidation in a northern saltmarsh (St. Lawrence Estuary, Canada). Can J Microbiol 2016; 62:530-7. [DOI: 10.1139/cjm-2015-0748] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Measurements of porewater O2, pH, and H2S microprofiles in intact sediment cores collected in a northern saltmarsh in the St. Lawrence Estuary (Quebec, Canada) revealed the occurrence of electrogenic sulfur oxidation (e-SOx) by filamentous “cable” bacteria in submerged marsh pond sediments in the high marsh. In summer, the geochemical fingerprint of e-SOx was apparent in intact cores, while in fall, cable bacteria were detected by fluorescence in situ hybridization and the characteristic geochemical signature of e-SOx was observed only upon prolonged incubation. In exposed, unvegetated creek bank sediments sampled in the low marsh in summer, cable bacteria developed only in repacked cores of sieved (500 μm), homogenized sediments. These results suggest that e-SOx is suppressed by the activity of macrofauna in exposed, unvegetated marsh sediments. A reduced abundance of benthic invertebrates may promote e-SOx development in marsh ponds, which are dominant features of subarctic saltmarshes as in the St. Lawrence Estuary.
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Affiliation(s)
- Alexandra Rao
- Université du Québec à Rimouski, Institut des sciences de la mer, 310 allée des Ursulines, Rimouski, QC G5L 3A1, Canada
| | - Nils Risgaard-Petersen
- Center for Geomicrobiology, Section for Microbiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, DK-8000, Aarhus C, Denmark
| | - Urs Neumeier
- Université du Québec à Rimouski, Institut des sciences de la mer, 310 allée des Ursulines, Rimouski, QC G5L 3A1, Canada
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70
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Long-distance electron transfer by cable bacteria in aquifer sediments. ISME JOURNAL 2016; 10:2010-9. [PMID: 27058505 PMCID: PMC4939269 DOI: 10.1038/ismej.2015.250] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 11/19/2015] [Accepted: 11/25/2015] [Indexed: 11/23/2022]
Abstract
The biodegradation of organic pollutants in aquifers is often restricted to the fringes of contaminant plumes where steep countergradients of electron donors and acceptors are separated by limited dispersive mixing. However, long-distance electron transfer (LDET) by filamentous ‘cable bacteria' has recently been discovered in marine sediments to couple spatially separated redox half reactions over centimeter scales. Here we provide primary evidence that such sulfur-oxidizing cable bacteria can also be found at oxic–anoxic interfaces in aquifer sediments, where they provide a means for the direct recycling of sulfate by electron transfer over 1–2-cm distance. Sediments were taken from a hydrocarbon-contaminated aquifer, amended with iron sulfide and saturated with water, leaving the sediment surface exposed to air. Steep geochemical gradients developed in the upper 3 cm, showing a spatial separation of oxygen and sulfide by 9 mm together with a pH profile characteristic for sulfur oxidation by LDET. Bacterial filaments, which were highly abundant in the suboxic zone, were identified by sequencing of 16S rRNA genes and fluorescence in situ hybridization (FISH) as cable bacteria belonging to the Desulfobulbaceae. The detection of similar Desulfobulbaceae at the oxic–anoxic interface of fresh sediment cores taken at a contaminated aquifer suggests that LDET may indeed be active at the capillary fringe in situ.
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71
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Sulu-Gambari F, Seitaj D, Meysman FJR, Schauer R, Polerecky L, Slomp CP. Cable Bacteria Control Iron-Phosphorus Dynamics in Sediments of a Coastal Hypoxic Basin. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:1227-1233. [PMID: 26720721 DOI: 10.1021/acs.est.5b04369] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Phosphorus is an essential nutrient for life. The release of phosphorus from sediments is critical in sustaining phytoplankton growth in many aquatic systems and is pivotal to eutrophication and the development of bottom water hypoxia. Conventionally, sediment phosphorus release is thought to be controlled by changes in iron oxide reduction driven by variations in external environmental factors, such as organic matter input and bottom water oxygen. Here, we show that internal shifts in microbial communities, and specifically the population dynamics of cable bacteria, can also induce strong seasonality in sedimentary iron-phosphorus dynamics. Field observations in a seasonally hypoxic coastal basin demonstrate that the long-range electrogenic metabolism of cable bacteria leads to a dissolution of iron sulfides in winter and spring. Subsequent oxidation of the mobilized ferrous iron with manganese oxides results in a large stock of iron-oxide-bound phosphorus below the oxic zone. In summer, when bottom water hypoxia develops and cable bacteria are undetectable, the phosphorus associated with these iron oxides is released, strongly increasing phosphorus availability in the water column. Future research should elucidate whether formation of iron-oxide-bound phosphorus driven by cable bacteria, as observed in this study, contributes to the seasonality in iron-phosphorus cycling in aquatic sediments worldwide.
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Affiliation(s)
- Fatimah Sulu-Gambari
- Department of Earth Sciences, Geochemistry, Faculty of Geosciences, Utrecht University , Utrecht, The Netherlands
| | - Dorina Seitaj
- Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research , Yerseke, The Netherlands
| | - Filip J R Meysman
- Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research , Yerseke, The Netherlands
| | - Regina Schauer
- Center for Geomicrobiology and Section for Microbiology, Department of Bioscience, Aarhus University , Aarhus, Denmark
| | - Lubos Polerecky
- Department of Earth Sciences, Geochemistry, Faculty of Geosciences, Utrecht University , Utrecht, The Netherlands
| | - Caroline P Slomp
- Department of Earth Sciences, Geochemistry, Faculty of Geosciences, Utrecht University , Utrecht, The Netherlands
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